Optoelectronic system comprising several sections having respective functions coupled by evanescent coupling and production process

Abstract

An optoelectronic system comprising at least three sections corresponding to specific respective functions and having different respective band gap energies, at least for the adjacent pairs of sections. These three sections consist of at least two layers superposed by epitaxy. The upper layer is etched in order to define said sections in the form of two separate end sections defined in the upper layer on each side of an intermediate section defined in the lower layer, and to allow coupling between the intermediate section and each of the end sections which flank it, by evanescent coupling. The length of the intermediate section is such that the product K×L, in which K represents the coupling coefficient of a grating of the intermediate section, is one of the order of 1.

What is claimed is:  
     
       1. Optoelectronic system comprising at least three sections (A, B, C) corresponding to specific respective functions and having different respective band gap energies, characterized in that these three sections consist of at least two layers ( 20 ,  30 ) superposed by epitaxy, the upper layer ( 30 ) being etched in order to define said sections in the form of two separate end sections (A, C) defined in the upper layer ( 30 ) on each side of an intermediate section (B) defined in the lower layer ( 20 ), and to allow coupling between the intermediate section (B) and each of the end sections (A, C) which flank it, by evanescent coupling, in which system the length (L) of the intermediate section (B) is such that the product (K×L), in which (K) represents the coupling coefficient of a grating of the intermediate section (B), is of the order of 1. 
     
     
       2. System as claimed in  claim 1 , characterized in that the length (L) of the intermediate section (B) is between 50 and 800 μm, preferably between 100 and 500 μm, very advantageously between 150 and 400 μm and very preferably about 200 μm. 
     
     
       3. System as claimed in  claim 1 , characterized in that the intermediate section (B) comprises a Bragg grating. 
     
     
       4. System as claimed in  claim 1 , characterized in that the upper layer ( 30 ) comprises three sections (A, C and E) placed respectively on each side of two intermediate sections (B and D) provided in the lower multilayer ( 20 ). 
     
     
       5. System as claimed in  claim 1 , characterized in that it constitutes an integrated laser-guide-modulator source. 
     
     
       6. System as claimed in  claim 1 , characterized in that it constitutes a device chosen from the group comprising optical transmission means with NRZ or RZ type output, distribution means or radio-on-fiber means such as a BLU circuit. 
     
     
       7. System as claimed in  claim 1 , characterized in that the lower multilayer ( 20 ) constitutes a passive guide centered around 1.3 μm. 
     
     
       8. System as claimed in  claim 1 , characterized in that it comprises two modulators (C and E) in the upper multilayer ( 30 ), a first modulator (C) forming a pulse generator and a second modulator (E) serving for coding. 
     
     
       9. System as claimed in  claim 1 , characterized in that the lower multilayer ( 20 ) comprises a GaInAsP-based active layer. 
     
     
       10. System as claimed in  claim 1 , characterized in that the lower multilayer ( 20 ) constitutes an active layer based on multiple quantum wells. 
     
     
       11. System as claimed in  claim 1 , characterized in that the lower multilayer ( 20 ) comprises an active layer ( 22 ) flanked by two InP-based layers ( 21 ,  23 ). 
     
     
       12. System as claimed in  claim 1 , characterized in that the lower multilayer ( 20 ) is coated with a stop layer ( 24 ), for example based on InP. 
     
     
       13. System as claimed in  claim 1 , characterized in that the upper multilayer ( 30 ) comprises an active layer ( 32 ) based on multiple quantum wells. 
     
     
       14. System as claimed in  claim 1 , characterized in that the upper multilayer ( 30 ) comprises an active layer ( 32 ) flanked by GaInAsP-based layers ( 31 ,  33 ). 
     
     
       15. Process for producing a system as claimed in  claim 1 , characterized in that it comprises steps consisting in: 
       i) depositing two superposed muitilayers ( 20 ,  30 ) on a substrate ( 10 ) by epitaxy;  
       ii) etching the upper multilayer ( 30 ) down to a stop layer ( 24 ) located at the top of the lower multilayer ( 20 ) in order thus to separate at least two end sections (A, C) in the upper multilayer ( 30 ) so as to allow evanescent coupling between the intermediate section (B) and each of the end sections (A, C) which flanks it.  
     
     
       16. Process as claimed in  claim 15 , characterized in that it furthermore includes the step consisting in carrying out a specific treatment on the intermediate section (B). 
     
     
       17. Process as claimed in  claim 16 , characterized in that the specific treatment consists in etching a Bragg grating in the intermediate section (B). 
     
     
       18. Process as claimed in  claim 15 , characterized in that it furthermore includes the step consisting in depositing a material, for example based on InP, over the entire wafer of the system. 
     
     
       19. Process as claimed in  claim 15 , characterized in that it furthermore includes the step consisting in depositing electrodes on the lower surface of the substrate and on the upper surface of the end sections (A, C, E).